i went through this for a few months and finally decided - and bought- an M5.
better value for money, nice electronic gadgets, just as fast (at least on straights...maybe not quite as fast on mountain roads and i do not care about the nuerburgring), good looking, great interior, practical car etcetcetc. i have the M5 now for almost four months, did 8K km
with it and still like it a lot. but here comes my big but......recently i have found myself testdrinving a lambo gallardo, porsche 991S, a ferrari 458 and a mclaren. why did i do this? well, the M5 in all its perfection is just not involving enough at legal speeds, and not even at those speeds which do not immediately threaten your license if caught. driving it is a bit like playing a video game. seems the car does the job for you anyway.
now i always get out of the comfort modes when i get in the car, use at least the M1 button, which i have programmed to sporty settings. then things improve somewhat for me at least subjectively.
do i regret having bought the M5? no. would i buy it again? no, i'd go for the porsche 991 C4S, which is a very nice compromise in practicality and sportyness between lambo, ferrari, mclaren on one side and the M5 on the other side. would i drive faster with any of those cars? no, but i would have more fun.
but in all earnest, you cannot go wrong with either of those cars,